Ammonium bicarbonate, with the chemical formula NH4HCO3, is a chemical compound composed of ammonium ions (NH4+) and bicarbonate ions (HCO3-). It is a white, crystalline solid that is soluble in water and has a slightly ammoniacal odor.

Ammonium bicarbonate has several key properties and uses, including:

1. Baking Agent: Ammonium bicarbonate is used as a leavening agent in baking. When heated, it decomposes into ammonia (NH3), carbon dioxide (CO2), and water (H2O). The release of carbon dioxide gas during baking causes the dough or batter to rise, resulting in a light and airy texture in baked goods like cookies and crackers.
2. pH Buffer: Ammonium bicarbonate acts as a pH buffer, helping to stabilize the pH of solutions and prevent drastic changes in acidity or alkalinity.
3. Textile and Dyeing Industry: It is used in the textile and dyeing industry as a mild alkali to treat fabrics and aid in the dyeing process.
4. Chemical Synthesis: Ammonium bicarbonate serves as a reactant in various chemical synthesis processes to produce other compounds.
5. Neutralizing Agent: In some applications, ammonium bicarbonate is used as a neutralizing agent for acidic substances.

It’s important to note that ammonium bicarbonate can release ammonia gas when heated or exposed to moisture, and it can also react with acids to produce carbon dioxide gas. Therefore, it should be handled with care, and adequate ventilation should be provided when using it in baking or other applications.

In recent years, the use of ammonium bicarbonate in the food industry has decreased due to safety concerns related to the potential presence of residual ammonia and the development of alternative leavening agents with better performance and stability. Other leavening agents like baking soda (sodium bicarbonate) and baking powder are more commonly used in modern baking practices.